It occurs pretty regularly in coal gas, and also in crude American petroleum, in which it is absorbed by the liquid hydrocarbons.

Ethane is a colourless and odourless gas of density 1.036; it has been liquefied at a pressure of 46 atmospheres at 4°. It is nearly insoluble in water, but soluble in a little less than its own volume of alcohol. By action of diffused daylight on a mixture of equal volumes of chlorine and ethane, there results, as first substitution-product, monochlor-ethane or ethylic chloride:

from which all the other ethylic compounds can be prepared. At the same time, especially when the chlorine is in excess, substitution-products richer in chlorine are formed.

153. Occurs in crude petroleum, and is obtained from the propyl compounds in a similar manner to ethane, most easily by action of zinc and hydrochloric acid upon both propylic iodides :

CH3

CH2

2CH2 + 2Zn + 2HCl = ZnI2+ ZnCl2 + 2CH2

CHI+2Zn + 2HCl = ZnI2+ ZnCl2 + 2CH2

CH3

Isopropylic iodide.

2

CH3

Without doubt the same body is obtained by heating a mixture of zinc methyl with ethylic iodide, or of zinc ethyl with methylic iodide :

Propane is a colourless gas, which liquefies below -20°, and of which six volumes are absorbed by one volume of alcohol. By action

of chlorine in diffused daylight there result, as the first substitutionproducts, the isomeric compounds:

propylic chloride, CH,, and isopropylic chloride, CHCI

154. As four carbon atoms can combine in two different ways to form a tetra-carbon nucleus :

two butanes can exist, and both have been prepared.

Normal butane, butylic hydride, diethyl, or propyl-methyl, occurs in crude petroleum, and is formed, as diethyl, by action of zinc or sodium upon ethylic iodide, or by the decomposition of zinc ethyl by this latter in sealed tubes heated to at least 150°:

Zn CH2.CH3 CH3.CH2I
CH2CH3CH.CHI

=

ZnI2+2CH3.CH2.CH2.CH3.

Ethylene and ethane are formed as secondary products during this reaction, one ethyl group, with double linking of its own carbon atoms, yielding hydrogen to the other :

On opening the cooled tube, which contains the butane liquefied by the pressure, a mixture of both gases is given off with great violence; later the butane evaporates, and can be condensed in a vessel cooled by a mixture of ice and salt.

Butane is, at ordinary temperatures, a colourless gas of ethereal odour, and of density 2.046; it becomes liquid at + 3° under a pressure of 2 atmospheres; its boiling point is about + 1°. It is nearly insoluble in water, pretty readily soluble in alcohol, this latter absorbing 18 times it own volume at 14°.

Isobutane, isobutylic hydride, or trimethyl methane, isomeric with the foregoing, is obtained by action of zinc and water upon the iodide from trimethyl carbinol:

CH3 CH3

20I + 2Zn + 2H2O = Zn(OH)2 + ZnI2 + 2

CH3

CH3 CH3

CH

CH3

It is a colourless gas, which is condensable to a liquid at -17°.

Pentanes, C5H12.

155. Corresponding to the three forms of a pentacarbon nucleus, three pentanes may exist, namely:

Both the former exist in American petroleum, and are obtainable therefrom by fractional distillation.

Normal pentane is also found in the light tar oils, from the distillation of cannel coal; it is a mobile colourless liquid, which boils at 37°-39°.

The boiling point of the closely analogous isopentane is about 30°; it is prepared synthetically by the decomposition of fermentation amylic iodide with zinc and water. It mixes in every proportion with alcohol, but not with water. At 24° it is still liquid. The density of the liquid is 626.

Tetramethyl methane results from the action of zinc methyl on tertiary butylic iodide :

2CH3-CI + Zn(CH3)2 = ZnI2 + 2CH,—C—CH,

as a colourless mobile liquid, which boils at + 9.5°, and solidifies to a crystalline mass at

20°.

Hexanes, C6H14.

156. The hexane formula admits of five isomeric modifications:

C<CH3
CH3
Diisopropyl,

a dimethyl butane.

CH2

1. Normal hexane is obtained by action of zinc and water, or of zinc and hydrochloric acid, upon secondary normal hexylic iodide, CH3CH2CH2CH2.CHI.CH, (which results from the action of hydriodic acid upon mannite), as a colourless liquid, boiling at 69°-70°, and of sp. gr. 663 at 17°. It is also prepared by decomposition of an ethereal solution of propylic iodide by sodium:

2CH3.CH2.CH2I + Na2 = 2NaI + CH3.CH2.CH2.CH2.CH2.CH3, and occurs in petroleum and light coal-tar oil.

2. a Isohexane is obtained, as ethyl-isobutyl, by action of sodium on an ethereal solution of a mixture of ethylic and isobutylic iodides:

CH2.CH,I + I.CH2.CH. {CH3 + Na2 = 2NaI

it boils at 62°, and has sp. gr. 7011 at 0°.

3. Isohexane has not yet been prepared.

4. Diisopropyl is obtained by de-iodising ispropylic iodide in ethereal solution by sodium:

CH

"CH3

CHI+ Na2 2NaI + CH3>CH-CH-CH3

=

as a colourless liquid, boiling at 58° and having sp. gr. 6769 at 10°. 5. Trimethyl-ethyl methane is prepared by action of zinc ethyl upon tertiary butylic iodide :

CH3

CH3

2CH,—CI + Zn(CH2.CH3)2 = ZnI, + 2CH3-C-CH2.CH,

CH3

It boils at 43°-48°.

CH3

Higher Homologues.

157. The number of possible isomers of every member of these series increases with the increase of the number of carbon atoms in the nucleus; but few of them, however, are known, and will now be shortly noticed.

Heptanes, CH16-Normal heptane,

CH3-CH2-CH2-CH2-CH2-CH2-CH3,

is contained in coal-tar oil and in petroleum; it is a liquid boiling at

97.5.

CH3 is obtained as ethyl

a Isoheptane, CH ̧.CH2.CH2.CH2.CH.CH2

isoamyl, by decomposition of a mixture of fermentation amylic iodide and ethylic iodide by sodium, as an oil boiling at 88°-90°. Dimethyl-diethyl methane or carb-dimethyl-diethyl,

CH2.CH3 results from the action of zinc ethyl upon ace

CH3>C<CH2CH3'

CH

tonylic chloride:

CH.CH3

or CH(C2H5)3, is

Triethyl methane, CH3.CH2.CH<CH,CH3

formed amongst other products by warming ethylic orthoformate with zinc ethyl :

2CH.(O.C2H3)3 + 3Zn(C2H5)2 = 3Zn(O.C2H5)2 + 2CH.(C2H5)3 Ethylic orthoformate. Zinc ethyl. Zinc ethylate.

It is a colourless, faint-smelling liquid of sp. gr. 689 at 27°, and boiling at 96°.

Octanes, CH18-Normal octane,

CH3-CH2-CH2-CH2-CH2-CH2-CH2-CH3,

or dibutyl, is formed from two molecules of normal butylic iodide (CH3-CH-CH2-CH2I) by de-iodising with sodium; it boils at 123°-125°, and has the sp. gr. 7032. It is also obtained from normal octyl alcohol, and from methyl-hexyl carbinol, and occurs in mineral oil.

CH3'

Diisobutyl, CH3CH–CH2 CH3>CH-CH-CH-CH-CH3, is prepared from isobutylic iodide and sodium, as a liquid boiling at 109°, and of sp. gr. .7057.

Nonanes, C,H20.-There are two known, namely, isobutyl-isoamyl, CH3 CH3>CH.CH2CH2. CH2. CHCH, prepared from the iodides of the respective alcohol radicals, which boils at 132°, and a body boiling at 130°, obtained in small quantity by action of sodium amalgam upon isopropylic iodide :

3

CH2

CH3

CH2-CH

CH3

This may be termed propylene diisopropyl, the group CH-CH-CH3 being the radical of the propylene compounds.

A third, probably normal nonane, occurs in petroleum, and also in the mixture of hydrocarbons obtained by the action of heat on solid paraffin; it boils at 147°-148°; sp. gr. 7279 at 13.5.

Decanes, C10H22.- One decane has been known for a long time under the name of diamyl, more correctly diisoamyl. It is prepared from fermentation amylic iodide by action of zinc or sodium: